The U.S., UK, Denmark, and other nations have demanded further action, including heightened surveillance, regarding the rapidly expanding practice of unregulated oil transfers at sea. This is because concerns over potential pollution are growing, according to a study filed to the U.N..

“These transfers threaten the rule-based system of international law and raise the danger of contamination for States that are coastal and close. The article stated that this poses a danger to international efforts to stop ship-related pollution.

The paper was submitted to United Nations shipping agency, the International Maritime Organization (IMO), by the member states ahead of a major marine environment protection committee session in July. It was also backed by Australia, Canada, Spain and Ukraine.

Hundreds of “ghost” tankers, which are not fully regulated, have joined this opaque parallel trade over the past few years, carrying oil from countries hit by Western sanctions and restrictions, including Russia and Iran.

The number of incidents last year, including groundings, collisions and near misses involving these ships reached the highest in years, a Reuters investigation showed.

“These risky practices, although under the jurisdiction of a flag state, unjustly expose national and local governments and authorities to paying for response and clean-up costs and compensating victims,” the paper said.

Tactics used by such ships include switching off tracking transponders, faking locations and also conducting ship-to-ship (STS) operations at locations outside of authorised transfer zones and sometimes in poor weather to conceal activities.

The paper, which will be discussed at the IMO session, said deceptive shipping practices were also “serious threats to the safety and security of international shipping”, including crew members.

The countries recommended that when flag states became aware of such practices they should step up inspections of those vessels and boost monitoring of activity including around territorial waters.

Ship insurer West said in a recent advisory that it would agree to cover STS operations by ships subject to certain provisions, including “no geographical deviation”. It also said transfers need to take place in good weather, in a dedicated STS transfer area and under the supervision of a qualified mooring specialist.